Week 8 Flashcards
Endotherms
When a body generates their own internal body heat and do not rely on the energy of the sunlight to warm their body
Homeotherms
Humans maintain their body temperatures within very narrow limits despite wide fluctuations in ambient temperature and therefore are homeotherms
Where is the control centre for regulating body temperature
Hypothalamus
Body temperature is ______ during the night and ________ during the day
Body temperature is lowest during the night and highest during the day
When do women experience higher body core temperature and why
It is higher during the second half of the menstrual cycle due to the effects of the hormone progesterone
Mechanisms of heat exchange
Radiation from the sun
Evaporation of sweat
Convection from air movement
Conduction to clothing
How does the body generate heat
Shivering
Decreased skin blood flow to the periphery
Behavioural choices (clothing)
How does the body cool itself down
Sweating
Vasodilation - heat leave through the skin to the surroundings
Behavioural - using/drinking water
Thermoneutral zone
The range of temperatures where the body can maintain its core temperature solely by regulating dry heat loss
How does shivering generate heat
Nerve impulses are sent to the hypothalamus to the skeletal muscle to bring about muscle contractions that generate heat
What happens when body temperature increases
Thermosensors in the brain sends signals through the CNS to adrenal medulla to dilate blood vessels and to cause sweat glands to secrete fluid. Vasodilation allows heat to leave the body through the skin (heat is lost to environment - body temp returns back to normal)
How does sweating work
Sweat glands are innervated by cholinergic nerve fibres via stimulation of muscarinic receptors
Circulating catecholamines can also stimulate sweat production
What happens when body temperature decreases
Blood vessels constrict
Heat stays at the core
Swat glands so not secrete fluid (heat is conserved) and shivering generates heat (heat is generated)
Vasoconstriction happens as a result of
Norepinephrine acting on adrenergic receptors
Hunting reaction
During long exposure to cold the skin circulating will often show intermittent periods of vasodilation
It is considered to be a protective mechanism against ischaemic injury (frostbite)
